I thought I once saw a thread about that but as I couldn't find it, I'll open a new one. In case someone knows where the other thread is, please let me know or if you have moderation rights, just move this post there

The German space magazine "Raumfahrt Concret" published some interesting numbers about mining on the Moon.

The baseline figure was to get 1 kg of Helium-3 for which you have to process 105 tonnes of Regolith (Lunar soil).

The titles of the threads in the Technology section about lunar mining or referring to it are

Lunar production site to be seen on the horizon?Lunar ISRUProduction of metals on the Moon - problems, solutions?Several oxygen-containing dusts?

There also is at least one thread about it in the Latest News section. "At least one" - in that section there also is a thread about Shackleton Crater Company as far as I remember. That company plans to mine not only hydrogen and water but methane also.

I am surprised by the amount of volitiles present, espesially ones containing hydrogen. Since Hydrogen is often a limiting factor for a moon based economy, I find these figures encouraging. I believe that in time most heavy industry and mining will move to the moon, where enviromental impact statement is... simpler.

Now that you mention it, I am surprised too. 105 metric tons is 105,000 kg and 6,100kg of hydrogen is 5.8% of that. That can't be right, so I googled "hydrogen in apollo lunar material" to get this source:
http://www.permanent.com/l-minera.htmThe table says there is 51 ppm hydrogen on average in Apollo 11 samples. That is 0.0051% or 5.355 kg in 105 tons. It also says there is more nitrogen than hydrogen, not less as the table above says. It also shows no water at all. So I question the accuracy of the source of that data.

Or maybe those kilograms should be grams. That would make more sense. That 5.8% hydrogen would become 0.0058% if it is 6,100 grams instead of kilograms, which is more plausible.

I wondered that too of course but I double-checked it in the magazine that I posted it as it was there but it's of course possible that there was an error in translating and setting the Russian original into German.

On the other side there's a sentence in the text "Auf 1kg Helium-3 entfallen etwa 18 t Begleitgase [...]" - "There are about 18 t of carrier gases on 1 kg of Helium-3"

They list one example:

Ilmenite (Feo, TiO2) is processed. They say up to 10% of the moon "soil" are that stuff:

Bugger, I thin if it was 1050 tons instead of 105 the report would make more sence. I that's the case there are still enough volitiles in the ground to support a moon economy without the need for raw material export. If were a miner for me SiO2 would be just junk. It is the metal ores that would interest me, the fact that you also get other stuff from regolith is just a bonus. I think economically the Moon should be the mining center of solar system. It is by far the closest to near Earth space in Delta-V and metal ores are all over the place in concentrations that would make most jaded prospectors jelous.

Just curious which metals would be most common on the Moon. Fe and Ti seem high on the list although I am surprised that Al hasn't been mentioned yet.

There is plenty of oxygen and aluminum on the Moon. Aluminum could be used as a fuel with LOX as the oxidizer. The engineering problems have not been solved though. I would think you could make a kind of hybrid engine with a solid aluminum fuel grain and flow LOX to it like SS1 did with rubber and nitrous oxide, but I think the surface area needed would require the aluminum to be an impossibly convoluted shape. I have also heard of powdered aluminum being suspended in LOX successfully. But not much work is being done in this area.

There is plenty of oxygen and aluminum on the Moon. Aluminum could be used as a fuel with LOX as the oxidizer. The engineering problems have not been solved though. I would think you could make a kind of hybrid engine with a solid aluminum fuel grain and flow LOX to it like SS1 did with rubber and nitrous oxide, but I think the surface area needed would require the aluminum to be an impossibly convoluted shape. I have also heard of powdered aluminum being suspended in LOX successfully. But not much work is being done in this area.

Powdered Aluminum is the primary fuel in the Space Shuttle, SRBs. It is conceivable that it could be sintered with a powdered glass binder in a hybrid rocket motor to avoid rare materials on the Moon. With LOX, this would be a "relatively conventional" hybrid motor.

I am also encouraged by the listed numbers for Lunar Hydrogen. Oxygen is of course one of the most common and easily recovered materials on the Moon (even if it takes more solar energy than the NASA Challenge Prize permits to extract it). This level of extractable Hydrogen would easily make up for processing losses. (I was envisioning "Hydrogen Farms" using a thin layer of evaporated Titanium on the Lunar surface to capture Hydrogen in the solar wind over a period of time. The Titanium Hydride would be periodically harvested and the area "reseeded" with a new film of Titanium.)